Applying fungicides to non-disease resistant wheat could return from $2 to $3 for every $1 invested.
“Plant disease is a limiting factor in wheat production in Northeast Texas,” says Jim Swart, Extension integrated pest management specialist at Commerce. Leaf rust and stripe rust are the primary culprits, Swart said during a recent small grains field day in Prosper.
Swart says from 25 to 30 trials looking at fungicide application and wheat yields indicate that treating non-resistant wheat is profitable. “We're trying to predict when to spend money. We looked at susceptible varieties and application timing.”
He says resistant varieties remain “the first line of defense for wheat disease. But races of rust change every three years or so. They change faster than we can develop new wheat varieties, so we need to keep some of the stronger varieties and apply fungicides.”
He says fungicide application timing may be critical. “Sometimes stripe rust comes in early and one application is not adequate. We need to split fungicide treatments — one when we first see the disease and another about three weeks later. That should give us from 25 to 40 days of protection.”
Swart says farmers have good materials available to manage rust diseases. “A fungicide is a profitable tool. The $1 farmers spend in early April makes them an extra $2 or $3 in early June. It's a good investment.”
He says a model for determining application timing is an ongoing effort.
“We also point out that fungicides do not enhance yields but protect yields. Spraying resistant varieties is a waste of money, but spraying susceptible ones pays off.”
Swart says efforts include scientists from Texas A&M-Commerce and College Station.
Ron French, Texas AgriLife Extension Plant Pathologist, says Texas wheat is susceptible to many leaf and seed diseases, but location within the state may dictate where certain problems occur. Some plant pathogens are more prevalent in certain areas than others.
French works out of Amarillo and says he saw no serious problems with leaf rust in the High Plains by early May. “We had no reports of either leaf rust or stripe rust in the Texas Panhandle.” Moisture is key for most fungal diseases and dry weather was prevalent throughout the Texas High Plains and Rolling Plains.
He says disease management should first include variety selection in order to target insects, diseases, and other production constraints in a field.
Then there are fungicides. He lists Tilt, Stratego, Headline, Quilt, Quadris and Bumper as mainstay products for rust control. New fungicides are expected to be labeled for the upcoming wheat production season.
French says several other diseases also cause trouble at times for wheat farmers, including wheat streak mosaic, High Plains virus, and a new virus called Triticum mosaic virus. All three are vectored (transmitted) by the wheat curl mite. “We've had problems this year with these viruses not only in the Texas High Plains (North Plains and parts of the South Plains), but also in the western part of the Rolling Plains,” he says. “It can be trouble. Once the plant is infected with one or more viruses, plants can show a significant decrease in yield or die.”
“Prevention is the key. Managing the wheat curl mite is our best option.” That should include destroying host plants for the mite, such as volunteer wheat and grassy weeds, at least three weeks prior to planting.
Resistant varieties are not available, but there are tolerant ones. “Most varieties will not hold up to these diseases.”
French says sometimes wheat has been infected with four viruses at the same time, the fourth being barley yellow dwarf, which is spread by green bugs and several other aphid species. “It could be bad in combination with other virus infections,” he says.
Most seed diseases are fungal and can include smuts and bunts. Best management advice is fungicide seed treatments, especially if wheat fields had such problems previously. He says loose smut can be treated with such fungicides.
“Sooty mold is not a big issue, but can be an indication of other problems. Seed may need to be treated for black point which can affect the embryo. Stinking smut (also known as common bunt) affects seed quality and its fishy smell can make it unfit for milling. It only takes a few seed per pound to be rejected by grain elevators and last year, some wheat seed was rejected.”